Technologies for improving a turning performance of a vehicle by controlling a driving force and a braking force of the vehicle automatically in cooperation with a steering operation of a driver to stabilize steering characteristics have been developed in the prior art. For example, Japanese Patent Laid-Open No. 2005-256636 discloses an invention relating to a vehicle stability control system for stabilizing an attitude and characteristics of a vehicle by reducing a disturbance resulting from an operation of a driver and a road disturbance. Specifically, according to the teachings of Japanese Patent Laid-Open No. 2005-256636, a disturbance and a physical quantity resulting from a running resistance are estimated, and an axle torque is corrected based on the estimated disturbance and physical quantity so as to allow a stability factor to follow a target value.
Meanwhile, Japanese Patent Laid-Open No. 2009-202621 discloses an invention relating to a stabilizer system for vehicle, which is capable of changing a roll suppressing force generated by a stabilizer bar by actuating an actuator. Specifically, Japanese Patent Laid-Open No. 2009-202621 discloses a fact that cornering powers of front and rear wheels are changed by a longitudinal load movement when the vehicle is accelerated or decelerated during turning of the vehicle, and as a result, steering characteristics (i.e., a stability factor) of the vehicle is changed.
According to the invention disclosed by Japanese Patent Laid-Open No. 2005-256636, the vehicle stability control system is configured to correct and control the driving force of the vehicle in a manner to allow the stability factor of the vehicle to follow the target value when the running vehicle is turned, in other words, in a manner to allow the vehicle to turn under the target steering characteristics. Therefore, a turning performance of the vehicle can be improved by thus improving the steering characteristics during turning of the vehicle. However, the driving force may be varied in a manner to generate an unintentional longitudinal acceleration by thus being corrected. Consequently, shocks may be generated to provide uncomfortable feeling to the driver. In order to reduce such shocks and uncomfortable feeling, it is considerable to reduce a correction amount of the driving force. In this case, however, the turning performance may not be improved effectively.